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Abstract:

The image pickup device includes display control means that controls
display means that is capable of displaying a live view, and control
means that drives and controls a focus lens in the correction mode on the
basis of the second focusing information or corrected first focusing
information, which is first focusing information that has been corrected
with a correction value for the first focusing information, the
correction value being calculated so as to correspond to a difference
between the first focusing information and the second focusing
information, the control means restarting displaying of the live view on
the display means, the displaying of the live view having been
interrupted in the correction mode.

Claims:

1. An image pickup device that includes first autofocus means, which
obtains first focusing information using a phase difference system, and
second autofocus means, which obtains second focusing information using a
contrast system, the image pickup device being capable of being set to a
correction mode for the first focusing information, the image pickup
device comprising: display control means that controls display means that
is capable of displaying a live view in which a photographed image is
displayed; and control means that drives and controls a focus lens in the
correction mode such that the focus lens enters a focused state using the
second focusing information or corrected first focusing information,
which is first focusing information that has been corrected with a
correction value for the first focusing information, the correction value
being calculated so as to correspond to a difference between the first
focusing information and the second focusing information, the control
means allowing the display control means to restart displaying the live
view on the display means, the displaying of the live view having been
interrupted in the correction mode.

2. The image pickup device according to claim 1, wherein the first
focusing information is obtained by converting a defocus amount into a
focus position, and wherein the second focusing information is obtained
by converting a contrast evaluation value into a focus position.

3. The image pickup device according to claim 1, wherein the display
means displays the correction value on a screen displaying the live view.

4. The image pickup device according to claim 1, wherein the display
means displays a confirmation button, with which the correction value is
confirmed, on a screen displaying the live view.

5. The image pickup device according to claim 1, further comprising
correction-value changing means with which the correction value is
changed.

6. The image pickup device according to claim 5, wherein the display
means displays a correction-value changing button, with which the
correction value is changed, on a screen displaying the live view.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Continuation of International Patent
Application No. PCT/JP2012/057456, filed Mar. 23, 2012, which claims the
benefit of Japanese Patent Application No. 2011-067813, filed Mar. 25,
2011, both of which are hereby incorporated by reference herein in their
entirety.

TECHNICAL FIELD

[0002] The present invention relates to an image pickup device that has a
function for correcting focusing information of autofocus means employing
a phase difference system, such as a single-lens reflex camera.

BACKGROUND ART

[0003] To date, there has been a case where, with usage of a single-lens
reflex camera that performs focusing using phase-difference AF, an
in-focus position changes due to the durability of a lens or a camera
body, and the focusing accuracy deteriorates as compared with that at the
time soon after the camera is purchased.

[0004] With regard to the lens, a case is conceivable where a stop
position of the lens, which is supposed to be driven to an accurate
in-focus position, is shifted by an occurrence of looseness attributable
to the durability.

[0005] With regard to the camera body, a case is conceivable where an AF
sensor determines a position that is away from an accurate in-focus
position as being the in-focus position because an angle of a mirror has
changed during driving of the mirror and thus the direction of light
incident on the AF sensor has changed.

[0006] In the above cases, a user has no choice but to bring the camera to
a service center and ask them to readjust the in-focus position in order
to restore the in-focus position to its original state.

[0007] For the purpose of solving the above problem, PTL 1, for example,
discloses a function with which an in-focus position obtained by using
phase-difference AF can be automatically corrected by using a contrast
system.

CITATION LIST

Patent Literature

[0008] PTL 1: Japanese Patent Laid-Open No. 2000-292684

[0009] According to PTL 1, however, it is not possible to confirm a
focusing accuracy obtained after the user has corrected the in-focus
position having been obtained by using phase-difference AF.

[0010] It is an object of the present invention to provide an image pickup
device whose focusing accuracy obtained after a user has corrected a
focusing state can be confirmed by the user when a correction value is
calculated, with which the focusing information having been obtained by
phase-difference-system autofocus means is corrected by using a contrast
system.

SUMMARY OF INVENTION

[0011] In order to achieve the above object, an image pickup device
according to the present invention is an image pickup device that
includes first autofocus means, which obtains first focusing information
using a phase difference system, and second autofocus means, which
obtains second focusing information using a contrast system, the image
pickup device being capable of being set to a correction mode for the
first focusing information, the image pickup device including display
control means that controls display means that is capable of displaying a
live view in which a photographed image is displayed, and control means
that drives and controls a focus lens in the correction mode such that
the focus lens enters a focused state using the second focusing
information or corrected first focusing information, which is first
focusing information that has been corrected with a correction value for
the first focusing information, the correction value being calculated so
as to correspond to a difference between the first focusing information
and the second focusing information, the control means allowing the
display control means to restart displaying the live view on the display
means, the displaying of the live view having been interrupted in the
correction mode.

[0012] Further features of the present invention will become apparent from
the following description of exemplary embodiments with reference to the
attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0013]FIG. 1 is a flowchart illustrating an AF calibration operation
according to the present invention.

[0015]FIG. 3 illustrates a screen displaying a live view for confirming a
focusing state.

[0016]FIG. 4 is a flowchart illustrating another AF calibration
operation.

[0017]FIG. 5 is a flowchart illustrating a correction-value changing
operation according to the present invention.

[0018]FIG. 6 illustrates a screen displaying a live view for changing a
correction value.

[0019] FIG. 7 is a sectional view of a schematic structure when mirrors
face downward.

[0020]FIG. 8 is a sectional view of a schematic structure when mirrors
face upward.

[0021]FIG. 9 is a flowchart illustrating another AF calibration
operation.

DESCRIPTION OF EMBODIMENTS

[0022] An embodiment of the present invention is described below.

Embodiment

[0023] As an image pickup device according to the present invention, a
digital single-lens reflex camera whose lens is replaceable will be
described.

[0024] FIG. 7 and FIG. 8 are sectional views of a schematic structure of a
digital single-lens reflex camera according to the embodiment.

[0025] An image-pickup optical system 10 housed in a lens 1 includes one
or multiple lens units, and is capable of changing a focal length or a
focus position by moving all or some of the lens units.

[0026] Lens driving means 11 is driving means that moves all or some of
the lens units included in the image-pickup optical system 10 to adjust a
focusing state.

[0027] Lens-state detecting means 12 is detecting means that detects a
focal length, that is, a zooming position and a focus position, of the
image-pickup optical system 10.

[0028] In addition, lens control means 13 is control means that controls
the entirety of the lens 1 including lens memory means 14 constituted by
a ROM or the like.

[0029] A connecting point 15 is a connecting point that is provided to the
lens 1 and the camera body 2, and when the lens 1 and the camera body 2
are fitted to each other, various types of information are communicated
through and power is supplied through the connecting point 15.

[0030] A main mirror 20 is constituted by a half mirror and is rotatable
in accordance with the operation state of the camera. When a subject is
observed through an optical viewfinder, the main mirror 20 is obliquely
disposed on a photographing optical path and deflects a light flux from
the lens 1 to guide the light flux to a viewfinder optical system, which
will be described later (FIG. 7). In the case of photographing or
displaying a live view, the main mirror 20 recedes from the photographing
optical path to allow the light flux from the lens 1 to be guided to an
image sensor 24, which will be described below (FIG. 8).

[0031] A sub-mirror 21 is rotated together with the main mirror 20. When
the main mirror 20 is obliquely disposed on the photographing optical
path, the sub-mirror 21 deflects the light flux that has been transmitted
through the main mirror 20 to guide the light flux to an AF sensor 22,
which will be described below (FIG. 7). In the case of photographing or
displaying a live view, the sub-mirror 21 recedes from the photographing
optical path by being rotated together with the main mirror 20 (FIG. 8).

[0032] The AF sensor 22 includes a secondary imaging lens, an area sensor
including multiple CCDs or CMOS sensors, and the like. The AF sensor 22
is capable of detecting a focal point by using a publicly-known phase
difference system.

[0033] A shutter 23 is used for controlling an incidence of a light flux
from the lens 1 on an image sensor 24, which will be described below. The
shutter 23 is normally in a closed state (FIG. 7), and enters an open
state at the time of photographing and displaying a live view (FIG. 8).

[0034] The image sensor 24 includes a CMOS image sensor and a peripheral
circuit of the CMOS image sensor.

[0035] A focusing screen 30 is disposed on a primary imaging area for the
lens 1. The focusing screen 30 has a Fresnel lens (condenser lens) on an
incident side, and a subject image (viewfinder image) is formed on an
emergent side of the focusing screen 30. A pentaprism 31 is used to
change a viewfinder optical path, and converts the subject image that has
been formed on the emergent surface of the focusing screen 30 into an
erect image.

[0036] An eye lens 32 is configured such that a diopter thereof is
adjustable to the vision of a user at the time when the user sees through
the viewfinder. Here, an optical system including the focusing screen 30,
the pentaprism 31, and the eye lens 32 is referred to as a viewfinder
optical system.

[0037] An AE sensor 33 is constituted by photodiodes that correspond to
multisegment zones in an image pickup area, and measures a brightness of
the subject image that has been formed on the emergent surface of the
focusing screen 30.

[0038] Camera control means 40 controls the camera body 2 as well as the
entirety of the camera including the lens 1. A microcomputer, for
example, is adopted as the camera control means 40. The AF sensor 22 and
the camera control means 40 constitute a first autofocus means
(focal-point detection means) that obtains first focusing information by
the phase difference system.

[0039] Digital control means 41 performs various control operations of
image data, and a memory controller, for example, is adopted as the
digital control means 41. The digital control means 41 can include
contrast-system autofocus means (focal-point detection means), which
detects a contrast of an image photographed by the image sensor 24 and
determines in-focus focus position (referred to as an in-focus position,
below) using a contrast evaluation value. The digital control means 41
constitutes second autofocus means (focal-point detection means) that
obtains second focusing information by using a contrast system.

[0040] The camera memory means 42 stores settings used for performing
various control operations, adjustment data, and the like, and a flash
ROM is adopted as the camera memory means 42.

[0041] A liquid crystal monitor 43 displays a photographed image or
various types of photographing information. The liquid crystal monitor 43
represents display means that displays a live view for confirmation of a
focusing status when set to an AF calibration mode (focusing-information
correcting mode).

[0042] Although not illustrated in FIG. 7 and FIG. 8, the liquid crystal
monitor 43 is provided with a SET button and a cancel button. When the
SET button is pressed while being displayed on the liquid crystal monitor
43, it is possible to perform operations, such as determination or
selection. When, on the other hand, the cancel button is pressed while
being displayed on the liquid crystal monitor 43, it is possible to
perform operations, such as to return to a previous state or to finish a
specific mode.

[0043] The digital control means 41 includes computing means that
calculates a correction value based on a difference between two outputs,
one of which is obtained by using a contrast system and the other one of
which is operated by the camera control means 40 using a phase difference
system on the basis of an output from the AF sensor 22. The difference
calculated by the computing means is stored in the camera memory means 42
as the correction value.

[0044] The camera according to this embodiment can be set to an AF
calibration mode in which the camera calculates and stores the
above-described correction value.

[0045] Hereinbelow, a function for making a correction for
phase-difference AF (AF calibration, below) will be described.

(Method of Moving Lens to In-Focus Position Obtained After Correcting
In-Focus Position Having Been Obtained by Phase Difference Detecting
System)

[0046]FIG. 1 is a flowchart illustrating an AF calibration operation
according to the embodiment.

[0047] Before starting a flow, an operation to determine a subject is
needed, first. After the subject is determined, an AF calibration is
started. A start screen at this time is as illustrated in FIG. 2.

[0048] The AF calibration is started by an instruction of a user. While
the camera is in the above-described AF calibration mode, the user
presses a start button 205 illustrated in FIG. 2 to start the AF
calibration. FIG. 2 illustrates a mode name display frame 201 that
displays AF microadjustment, which is an alternative name for the AF
calibration mode, a lens name 202, a calibration 203, a correction value
index 204, and a cancel button 206.

[0049] In Step S101, a subject is focused on by using the contrast
detection system (alternative name for the contrast system).

[0050] In Step S102, the camera control means 40 transmits a signal to the
lens control means 13 to move a focus lens to a predetermined position
via the lens driving means 11.

[0051] In Step S103, a contrast of an image signal obtained from the image
sensor 24 is detected by the digital control means 41.

[0052] In Step S104, the slight movement of the focus lens in Step S102
and the contrast detection in Step S103 are repeated until a
predetermined number N of times is reached.

[0053] In Step S105, the digital control means 41 determines a focus
position, at which an image signal having a contrast highest among N
detected results of contrasts is obtained, as an in-focus position, and
transmits a signal to the camera control means 40. The camera control
means 40 receives position information at this time from the lens-state
detecting means 12 via the lens control means 13 and forms in-focus
position information. In summary, a high contrast evaluation value that
satisfies certain conditions is converted into a focus position, which is
taken as an in-focus position.

[0054] In Step S106, the camera control means 40 causes the AF sensor 22
to detect a focal point by using phase-difference AF, and forms the
in-focus position information by adding a value to the focus position
information from the lens-state detecting means 12, the value being
obtained by converting a result detected at this time, i.e., a
focal-point shift amount (defocus amount), into an amount of driving of a
focus lens in an in-focus direction.

[0055] In Step S107, the camera control means 40 causes the digital
control means 41 to calculate an in-focus position correction value,
which is a difference between the in-focus position information
determined by the digital control means 41 as an in-focus position and
the in-focus position information obtained from among the detected
results of the AF sensor 22.

[0056] In Step S108, the in-focus position correction value calculated by
the digital control means 41 is stored in the camera memory means 42.

[0057] In Step S109, the in-focus position information formed in Step S106
is corrected with the in-focus position correction value stored in the
camera memory means 42.

[0058] In Step S110, the camera control means 40 transmits a signal to the
lens control means 13 to move the focus lens to the in-focus position,
which has been corrected in Step S109, via the lens driving means 11. In
this step, an amount of shift of the focal point (defocus amount)
obtained by using phase-difference AF is calculated, the amount of shift
of the focal point (defocus amount) is corrected with the in-focus
position correction value stored in the camera memory means 42, and the
focus lens is moved in accordance with the corrected value. The
calculation, the correction, and the movement are each performed at least
twice. With these operations being performed twice or more, it is
possible to eliminate a shift from a target position due to looseness of
a driving member (gear, motor, or another component) of the focus lens.

[0059] In Step S111, displaying of the live view, which has been
interrupted during the AF calibration mode, is restarted, so that a live
view image is displayed on the liquid crystal monitor 43. Since the focus
lens is moved in accordance with the in-focus position correction value
and the moving of the focus lens is performed at least twice in Step
S110, it is possible to display a live view that has a high focusing
degree.

[0060] A screen displaying a live view at this time is as illustrated in
FIG. 3. As the index 204 indicates the position of +10 in the example of
FIG. 3, the correction value displayed on the screen is +10. Here, a user
can confirm the correction value and the focusing accuracy corresponding
to the correction value by seeing the live view image screen displayed on
the liquid crystal monitor 43. FIG. 3 illustrates a confirmation button
207 that is displayed on the screen while the screen is displaying the
live view, and when the user presses the confirmation button 207, the
correction value is fixed.

[0061] The AF calibration is finished with these steps.

(Method of Moving Lens to In-Focus Position Obtained by Using Contrast
Detection System)

[0062] In Step S110, the focus lens is moved to a position obtained by
correcting the in-focus position having been obtained by using the
phase-difference AF. In this regard, the focus lens may be moved to an
in-focus position obtained by using a contrast detection system. An AF
calibration flow in that case is as illustrated in FIG. 4. The flow
illustrated in FIG. 4 follows the flow illustrated in FIG. 1.

[0063] An in-focus position obtained by using a contrast detection system
in Step S305 is stored in the camera memory means 42 or a RAM in advance
and is retrieved in Step S309 in FIG. 4.

[0064] In Step S310, the camera control means 40 transmits a signal to the
lens control means 13 to move the focus lens to the in-focus position,
having been retrieved in Step S309, via the lens driving means 11.

[0065] Here, description has been given of a method in Step S310 where a
lens is moved to the in-focus position obtained by using a contrast
detection system. In this regard, since the AF calibration is performed
to make a correction for the phase-difference AF, a method in Step S110
is preferable where the lens is moved to the in-focus position obtained
by making a correction for the phase-difference AF. This is because, even
though the lens is moved toward the in-focus position obtained by using a
contrast detection system, the live view is displayed while the focusing
degree is somewhat reduced compared with the case of the above-described
example due to the looseness of a driving member (gear, motor, or another
component) of the lens. However, the reduction of the focusing degree may
be allowed since the live view display is visually recognized through a
small rear monitor or a movable monitor, which is generally attached to a
camera.

(Method of Obtaining In-Focus Position by Using Phase-Difference
Detection System After Bringing Lens Close to In-Focus Position Obtained
by Using Contrast Detection System)

[0066] In Step 106 of FIG. 1, the in-focus position information is
obtained by using a phase difference system after the contrasts have been
detected and before the lens is driven. Here, the in-focus position
information may be obtained by using a phase difference system after the
lens is driven so as to come closer to the in-focus position in
accordance with the in-focus position information having been obtained by
using a contrast detection system in Step S105. The flow of the AF
calibration in this case is as illustrated in FIG. 4. The flow in FIG. 9
follows the flow in FIG. 1.

[0067] The lens is driven so as to come closer to the in-focus position
having been obtained by using a contrast detection system in Step S905 in
accordance with the in-focus position information (Step S920). Then in
Step S906, the in-focus position information is formed by using the phase
difference system.

[0068] According to the flow illustrated in FIG. 9, detection of the
in-focus position using the phase difference system can be performed with
a high accuracy. This is because an image obtained at this time is less
blurred than an image obtained at the time when driving of the lens for
contrast detection is finished. Thus, multiple calculations of an amount
of shift of the focal point (defocus amount) by using the
phase-difference AF and multiple corrections of an amount of shift of the
focal point (defocus amount), which have been made in Step S110 of the
flow in FIG. 1, become unnecessary. The calculation and correction may of
course be performed multiple times as illustrated in the flow of FIG. 1.

[0069] In this case, after the in-focus position information has been
obtained by using a phase difference system in Step S920, the in-focus
position information having been formed in Step S906 is corrected in Step
S909 with the in-focus position correction value stored in the camera
memory means 42. This step is performed similarly to Step S109 of FIG. 1.

[0070] In Step S910, in the same manner as in Step S110, the camera
control means 40 transmits a signal to the lens control means 13 to move
the focus lens to the in-focus position, having been corrected in Step
S909, via the lens driving means 11.

(Changing Correction Value by User)

[0071] Next, a case where a user changes a correction value after the AF
calibration has been performed will be described. FIG. 5 is a flowchart
illustrating that a correction value can be changed by a user.

[0072] In Step S501, a series of steps of the AF calibration operation
illustrated in FIG. 1 or FIG. 4 is performed. In this case, the screen
that displays a live view in Step S111 or Step S311 is as illustrated in
FIG. 6.

[0073] In Step S502, the user can change the correction value. The user
changes the correction value in the front direction or the rear direction
by pressing a correction-value changing button (frontward) 208 or a
correction-value changing button (rearward) 209, which is displayed on
the screen of FIG. 6. In the case where no change is needed, the user
confirms the correction value by pressing the confirmation button 207. At
this time, the user can change the correction value while confirming a
subject image displayed as a live view, since the displaying of the live
view is restarted in Step S111 of FIG. 1.

[0074] In Step S503, it is determined whether or not the correction value
has been changed in Step S502. In the case where the correction value has
been changed, the flow proceeds to Step S504. In the case where the
correction value has not been changed, the flow proceeds to Step S505.

[0075] In Step S504, the camera control means 40 transmits a signal to the
lens control means 13 in accordance with the amount of change of the
correction value to move the focus lens via the lens driving means 11. In
Step S505, the correction value is stored in the camera memory means 42.

[0076] In the above embodiment, the following effects can be obtained.

[0077] A user can confirm the accuracy of focusing performed by using the
phase-difference AF after the AF calibration, by driving the lens to the
in-focus position obtained by correcting the in-focus position having
been obtained by using the phase-difference AF, and then by displaying an
image at that time.

[0078] Further, since a user can change the correction value while
confirming the focusing accuracy, the user can perform a correction for
the phase-difference AF as intended.

[0079] Although means that includes the AF sensor 22 and the camera
control means 40 is described as the first autofocus means employing the
phase difference system, the present invention is not limited to this.
Phase-difference autofocus means employing an image-pickup-surface phase
difference system, in which focal-point detection pixels are arranged in
a focal-point detection area on an image pickup surface of the image
sensor 24, can also be employed as the first autofocus means.

[0080] The present invention is not limited to the above-described
embodiment, and can be changed or modified in various manners without
departing from the spirit or scope of the present invention. Thus, in
order to make the scope of the present invention known to the public, the
following claims are presented.

[0081] According to the present invention, a focusing accuracy obtained
after a user has corrected a focusing state can be confirmed by the user
when a correction value is calculated, with which the focusing
information having been obtained by phase-difference-system autofocus
means is corrected by using a contrast system.

[0082] While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is not
limited to the disclosed exemplary embodiments. The scope of the
following claims is to be accorded the broadest interpretation so as to
encompass all such modifications and equivalent structures and functions.